The present invention relates to an indwelling needle assembly used for fluid infusion, hemodialysis or the like. More specifically, the invention relates to a safety indwelling needle provided with a safety mechanism.
In recent years, there has arisen a problem of a risk of transmission of AIDS or hepatitis virus to medical personnel due to accidental puncture by a pointed edge of an injection needle or the like which is contaminated by blood. Therefore, in an indwelling needle assembly including an inner needle and an outer needle, a safety indwelling needle in which the inner needle is covered after use without putting a cap again thereon to prevent accidental puncture has been invented.
For example, there is disclosed a safety indwelling needle in which an inner needle is retracted within a needle cover and stored therein by a spring when a button provided on the indwelling needle is pushed after use (for example, Japanese Patent Laid-Open No. 52499/1998).
There is also disclosed a safety indwelling needle in which a spring-type needlepoint protecting means is disposed within an outer needle hub, and when an inner needle is drawn out, the needlepoint protecting means comes apart from the outer needle hub and covers a distal end of the inner needle (for example, Japanese Patent Laid-Open No. 102345/2002).
Furthermore, there is disclosed a safety indwelling needle in which a sliding cover provided on an inner needle is extended when the inner needle is drawn out from an outer needle so that the entire needle is stored within the cover (for example, Japanese Patent No. 3400550 and Japanese Patent Laid-Open No. 148270/1995).
In the safety indwelling needles provided with a safety mechanism in the related art, since the needlepoint protecting means for covering the inner needle drawn out from an outer needle unit is required to store the entire inner needle, the size of the indwelling needle itself is significant. Also, the safety indwelling needle provided with a spring as the needlepoint protecting means had a problem in that friction between the inner needle and the needlepoint protecting means is large by an urging force of the spring and a drawing-out resistance of the inner needle is also large. Therefore, a force required for drawing out the inner needle is increased and the usableness of the indwelling needle is deteriorated. Furthermore, even when the inner needle is protected by the needlepoint protecting member or the like, there is still a risk of re-projection of the needlepoint from the needlepoint protecting means.